Inductive communication system and method

ABSTRACT

A system and method communicate signals between a portable unit and a communications system. The portable device communicates with a base unit using inductive coupling. The base unit is further connected to a wider communication system such as a telephone network. Multiple, orthogonally arranged transducers are used in the base unit to provide a more complete magnetic field and to prevent mutual inductance nulls which are otherwise present in a magnetic field. The use of short-range inductive coupling minimizes the power requirements and limits interference with other sources. The inductive coupling may also be used to recharge a battery in the portable device.

RELATED APPLICATION(S)

[0001] This application is a continuation of U.S. application Ser. No.09/053,107, filed Apr. 1, 1998, which is a continuation of U.S.application Ser. No. 08/824,260, filed on Mar. 26, 1997, which is a FileWrapper Continuation of U.S. application Ser. No. 08/444,017 filed onMay 18, 1995, the entire teachings of all of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to short-range wirelesscommunication systems, and more particularly to systems utilizinginductive coupling.

[0004] 2. Discussion of the Related Art

[0005] When using a telephone, continually holding the handset to one'sear can be awkward. Also, holding the telephone interferes with the useof both hands for other work while trying to talk. In particular, theuse of cellular telephones, which has increased dramatically, caninterfere with the user's proper operation of an automobile. Varioustechniques have been used to overcome these difficulties.

[0006] Speakerphones allow one to talk while roaming around a room andusing one's hands. However, speaker volume can disturb others around theuser. They also cannot be used in close proximity to other speakerphonesdue to interference. They have limited privacy since the speakerbroadcasts the conversation to all within earshot. Typically, the usermust speak more loudly than normal to have proper reception at themicrophone. Also, they tend to have poor sound quality because the useris not near the microphone and acoustics in the room are poor.

[0007] Headsets have been another way to free up the hands of atelephone user. Typically, the headset includes an adjustable strapextending across the user's head to hold the headset in place, at leastone headphone located by the user's ear, and a microphone which extendsfrom the headset along and around the user's face to be positioned infront of the user's mouth. The headset is attached by a wire to thetelephone. Headsets have the disadvantages of being bulky and somewhatawkward to use. Although they permit hands free use of the telephone,the user has limited mobility due to the connecting wire.

[0008] Wireless headsets have also been developed which eliminate theconnecting wire to the telephone. The wireless headset uses radiofrequency (RF) technology or infrared technology for communicatingbetween the headset and a base unit connected to the telephone. The needfor communications circuitry and sufficient power to communicate withthe base unit increases the bulk and weight of the headset. Thisincreased weight can become tiresome for the user. One alternative hasbeen to attach the headset by a wire to a transmitting unit worn on thebelt of the user. As with wired headsets, the wire can becomeinconvenient and interfere with other actions by the user. Significantinterference rejection circuitry is also needed when multiple wirelessheadsets are used in close proximity.

[0009] Therefore, a wireless communication system for telephones isdesired with will provide greater convenience and comfort for the user.

SUMMARY OF THE INVENTION

[0010] The deficiencies of prior art systems are overcome by the presentinvention which, in one aspect, includes a short-range, wirelesscommunication system including a miniaturized portable transceiver and abase unit transceiver. The miniaturized portable transceiver sends andreceives information through magnetic induction to the base unit, whichmay also be portable. Similarly, the base unit sends and receivesinformation through magnetic induction to the portable transceiver. Theinformation can be voice, data, music, or video. Use of magneticinduction fields reduces the power requirements and thus allows asmaller size and greater convenience.

[0011] In another aspect of the present invention, the base unit mayinclude multiple, orthogonally arranged transducers for generatingmultiple magnetic fields. The multiple fields substantially eliminatesmutual inductance nulls between the base unit and portable unit whichresult at certain positions in a generated field. In another aspect ofthe present invention, the multiple transducers may be selectivelyoperated based upon a strongest signal, in order to limit powerconsumption.

[0012] In another aspect of the present invention, a headset containsthe miniaturized transceiver which communicates with the base unitthrough magnetic induction fields. The information sent between theheadset and the base unit may be voice or data. In another aspect of thepresent invention, the headset may be of the concha type in which thespeaker fits into the user's ear without a strap across the head and thetransceiving transducer is encapsulated into the microphone boom whichis short and straight along the user's cheek. In another aspect of theinvention, the base unit may be a portable telephone, which can beattached to the user, to further transmit communications from thewireless communication system to a cellular telephone network or acordless telephone unit.

[0013] In another aspect of the invention, the headset may fit in areceptacle in the portable base unit in order to recharge the battery inthe headset. In another aspect of the invention, the battery may berecharged via the magnetic inductive link between the base unit and theheadset.

[0014] With these and other objects, advantages and features of theinvention that may become apparent, the nature of the invention may bemore clearly understood by reference to the following detaileddescription of the invention, the appended claims and the severaldrawings attached hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 illustrates schematically the wireless communication systemof the present invention.

[0016]FIG. 2 illustrates a telephone handset as the base unit in thecommunication system of FIG. 1.

[0017]FIG. 3 illustrates a headset that is utilized as the portabledevice in the communication system of FIG. 1.

[0018]FIG. 4 illustrates schematically the transducer and electronics ofthe portable device.

[0019]FIG. 5 illustrates schematically the transducer and electronics ofthe base unit.

[0020]FIG. 6 illustrates an alternative transducer configuration for thebase unit.

DETAILED DESCRIPTION

[0021]FIG. 1 illustrates schematically a short-range magneticcommunication system 1 including a portable device 2 and a base unit 1,which connects to a long-range communication network 14. Containedwithin each of the base unit 1 and the portable device 2 is ashort-range miniaturized magnetic induction transceiver 11, 12, whichcan simultaneously transmit and receive communications signals 13. Thesesignals may be voice, audio, data, or video. The communications network14 may be any network in which it would be desirable for these signalsto be communicated over a terminal link without wires, such as atelephone network, personal communications, (PCS) network, specialmobile radio (SMR) network, computer system or network, and videoconferencing systems. The base unit 1 may any part of the communicationsnetwork 14 from which it would be desirable to communicate to anotherdevice without wires; for example, it may be a telephone handset, PCShandset, SMR handset, walkie-talkie, computer or computer peripheraldevices, personal digital assistant (PDA), or video game controller. Theportable device 2 may be any device from which it would be desirable tocommunicate without wires to a communications network; for example, itmay be a telephone headset or handset, portable computer or computerperipheral device, headphone, or video input device.

[0022] As illustrated in FIG. 2, one example of the base unit 1 is aportable telephone 10 having a plurality of number buttons 15 and aplurality of function buttons 16. A retractable antenna 17 communicateswith a cellular telephone network or a cordless telephone base unit. Theportable telephone 10 operates in a manner similar to that of anordinary cellular or cordless telephone handset. Signals are sent to andreceived from the telephone network in an ordinary manner. The portabletelephone 10 includes a transducer system 30 which communicates bymagnetic induction with headset 20, which operates as the portabledevice 2, to provide the outputs and inputs to the portable telephone10. The portable telephone 10 may also include a mouthpiece or earpiece(not shown) as in a regular telephone handset, allowing the user tochoose between a conventional method of operation and a hands-free useafforded by the headset 20.

[0023] The portable device 2 as a headset 20 is illustrated more fullyin FIG. 3. It includes a body portion 23 which houses a transducer 40and processing circuitry. A speaker 22 is connected to the circuitrywithin the body 23. An earpiece 21 next to the speaker 22 fits in theuser's ear to hold the unit in place and to allow the user to hearsounds from the speaker. A microphone boom 24 extends from the body 23several inches in order to place a microphone 25, located at the end ofthe boom 24, close to the user's mouth. Alternatively the transducer 40may be housed in the boom 24. A rechargeable battery 51 is also housedin the body 23 of the headset 20 to provide power to the headset. Otherfeatures may be optionally included in the headset 20, such as switcheror buttons for manually activating different modes. For example, acapacitive switch or push-button could be used to cause the headset 20to transmit a control signal to the portable phone 10 to activate mutingof the microphone. The portable phone 10 may include a receptacle 19 forreceiving and holding the headset 20. Depositing the headset in thereceptacle can provide a variety of functions, in addition tomaintaining the headset 20 and portable phone 10 together. A switch canbe disposed in the receptacle to terminate the telecommunication whenthe headset 20 is inserted or initiate the telecommunication when it isremoved. The receptacle may also include connections to recharge thebattery 51 in the headset 20.

[0024] The base unit 1 and portable device 2 communicate throughamplitude modulation of inductive fields, although other modulationmethods such as frequency or phase modulation could be employed. Duringuse, the distance between the portable device 2 and the base unit 1typically is short. Since the distance is short, only an inductive fieldis necessary, and little or no radiation occurs. This limits theoperating power, which allows a smaller size and weight for therechargeable battery 51 and, thus, the portable device 2. Furthermore,it limits interference between systems operating in close proximity.Therefore, interference rejection circuitry may be limited or notnecessary in the portable device 2.

[0025] The transducer system in the portable device 2 is illustratedschematically in FIG. 4. The transducer 40 preferably includes a ferriterod transducer having a ferrite rod 41 within a wire coil 42. The wiresfrom the transducer 40 are connected to a transceiver 27 havingtransmitter electronics 28 and receiver electronics 29. The transceiver27 connects to the portable device electronics 26, the nature of whichis dependent upon the function of the portable device 2. In the exampleof the portable device as a headset 20, the portable device electronicswould connect to a speaker 22 and a microphone 25. Transmission andreception can occur at different frequencies, which permits full duplexoperation. Alternatively, separate transmitting and receivingtransducers can be used.

[0026] The base unit 1 configuration is illustrated schematically inFIG. 5. The transducer system 30 includes three orthogonally disposedferrite rod transducers, each including a ferrite rod 31, 32, 33 and arespective coil 34, 35 and 36. The use of the orthogonally disposedtransducers overcomes the occurrence of mutual inductance nulls in theresulting inductive fields. The three transducers are connected tomultiplexer electronics 60 for selecting one or more of the transducersfor transmission and reception. Circuitry may be used to select thetransducer or transducers having the strongest signal for transmissionand reception to reduce the total power consumption of the device. Thetransmitter electronics 61 and receiver electronics 62 provide forprocessing of the communications signals from the base unit electronics70 and the portable device 2. As discussed above, for a portabletelephone 10, the conventional telephone speaker 71 and mouthpiece 72may be eliminated so that the portable telephone 10 solely uses theheadset 20 through the transducer system for communicating to the user.Switching circuitry (not shown) would be included to select between thespeaker 71 and microphone 72, and the headset 20. The switchingcircuitry could be included in the receptacle 19 so that the speaker 71and microphone 72 are disconnected when the headset 20 is removed.

[0027]FIG. 6 illustrates a second embodiment of the transducer systemfor the base unit 1. In the transducer 30 of FIG. 6, one of the ferriterod transducers is replaced with a loop coil transducer 37. A loop coiltransducer can replace any or all of the ferrite rod transducers. Theloop coil transducer 37 is disposed in the plane of the remainingferrite rod transducers. This creates a transducer system having adecreased depth. As illustrated in FIG. 2, the three orthogonaltransducers can be placed in a corner along the sides of the portabletelephone 10. Alternatively, the loop coil transducer 37 could be placedalong the back of the portable phone 10, so that it could made thinner.

[0028] Additionally, the transmission system can be used for chargingthe battery 51 of the portable device 2. The base unit 1 includes abattery charger signal generator 52 connected to the transmitter 61.This generator 52 produces a recharging signal which is sent through oneof the ferrite rod transducers in the base unit 1 to the ferrite rodtransducer 40 of the portable device 2. Since in the telephoneembodiment of FIG. 2, the headset 20 and transducer 40 have a knownorientation when in the receptacle 19, only one transducer in theportable telephone 10 needs to be energized to inductively transmit therecharging signal. As illustrated in FIG. 3, the wires from thetransducer 40 in the portable device 2 are connected to a batterycharger 50 which is used to charge the battery 51.

[0029] Although the communication system of the present invention hasbeen illustrated in connection with a concha type headset 20 and acellular or cordless telephone handset 10 as a base unit 1, it isreadily adaptable for other types of headsets and uses. The headset canbe of the over-the-head type, over-the-ear type, or binaural type. Thesystem can be used as a wireless connection to a conventional desktoptelephone. Such a system would operate in the manner discussed abovewith the cordless handset. Since several such units may be used in closeproximity, interference may become more of a problem. Therefore, thesystem can be designed to operate on various frequencies and can selectfrequencies for the transmission and reception which are unlikely tohave significant interference. Similarly, the system can be used with acomputer, either stationary or portable, for voice data entry, soundtransmission, and telephone functions. The system can also be used withother types of communication systems, including personal digitalassistants (PDA's), cordless phones, PCS and SMR cellular phones, twoway (video games), two-way half duplex (walkie-talkies, CBs), or two-wayfull duplex (phones). When the base unit is stationary and the user islikely to be at certain locations relative to the base unit, fewertransducers may be used in the base unit without encountering mutualinductance nulls. Alternative transducer systems may also be used forgenerating the inductive fields. Specifically, rather than a singletransducer for transmission and reception on different frequencies,separate transducers may be used.

[0030] Having thus described one illustrative embodiment of theinvention, various alterations, modifications, and improvements willreadily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to be within the spirit andscope of the invention. Accordingly, the foregoing description is by wayof example only and is not intended as limiting. The invention islimited only as defined in the following claims and equivalent thereto.

What is claimed is:
 1. A method of communicating information over awireless link, the method comprising: sensing a first magnetic fieldsignal on each of at least two transducer elements; providing a transmitsignal to be transmitted; and selectively applying the transmit signalto one or more of the at least two transducer elements in accordancewith a relative strength of the sensed first magnetic field signal totransmit a second magnetic field signal.
 2. A system for communicatinginformation over a wireless link, the system comprising: a first stationincluding at least two inductive transducer elements to receive amagnetic field from a second station, the first station including acircuit to detect a signal strength of the magnetic field as received oneach of the at least two transducer elements, the first stationselectively applying a transmit signal to the at least two inductivetransducer elements in accordance with the detected signal strength ofthe magnetic field to transmit to the second station.